Mr. Brown's Science Labs

The American lobster (Homarus americanus) is a cold-water crustacean that lives along the Atlantic coast from Labrador to North Carolina. Its body is divided into a head and thorax fused under a hard shell called the carapace, and a segmented abdomen ("tail"). Because the shell does not stretch, lobsters grow by molting — shedding the old shell and absorbing seawater to expand the new, soft shell underneath. A young lobster molts up to 25 times in its first 5–7 years before reaching legal harvest size.

For most of the 1900s, Long Island Sound supported one of the most productive lobster fisheries on the East Coast. New York and Connecticut lobstermen landed millions of pounds each year. Then, in the late summer of 1999, the fishery collapsed. Lobsters came up dead in the traps. Within months, the Sound's population had crashed by more than 90 percent, and the fishery has never recovered.

Scientists have identified three combined causes for the die-off. First, summer water temperatures in the bottom of the Sound rose above 20°C, which is the upper thermal limit for adult lobsters. Warm water lowers dissolved oxygen and stresses the animals. Second, mosquito-control programs sprayed pesticides containing methoprene and malathion to fight West Nile virus that same summer. These insecticides washed into the Sound and are toxic to lobsters because lobsters are arthropods, biologically related to insects. Third, weakened lobsters became susceptible to epizootic shell disease, a bacterial infection that eats lesions into the carapace and prevents successful molting.

Meanwhile, the lobster fishery in Maine has boomed. As ocean waters warm in the Gulf of Maine, lobsters have shifted their range northward into cooler water. Maine landings rose from about 20 million pounds in 1990 to over 100 million pounds by the 2010s. Maine lobstermen also follow strict sustainability rules: minimum size of 3.25 inches carapace length, a maximum size, and the practice of V-notching — cutting a small notch in the tail of any egg-bearing female before releasing her. A V-notched female is illegal to keep for life. Traps must include an escape vent that allows juvenile lobsters to crawl out before being hauled aboard.

For the lobstermen of Montauk, the lesson is clear. A fishery is a system that depends on water quality, climate, and the cooperation of the people who harvest it. Without all three, the boats stop coming back full.